Interstitial Lung Disease

Interstitial lung disease describes a group of lung diseases which affect the lung interstitium (= the tissue of the alveolar wall between the capillary endothelium and the alveolar epithelium) and share similar clinical and radiological features.

Diffuse parenchymal lung disease is synonymous with interstitial lung disease.

In 2002 the European Respiratory Society and American Thoracic Society produced the following classification of interstitial lung diseases:

  • ILD of known cause or association
    • Environmental - eg bird exposure
    • Occupational - eg silicosis, asbestosis
    • Drug-associated - eg amiodarone, methotrexate, cyclophosphamide, nitrofurantoin
  • ILD of unknown cause 
    • Idiopathic interstitial pnuemonias
      • Idiopathic pulmonary fibrosis (previously known as crytogenic fibrosing alveolitis)
      • IIP other than IPF eg crytogenic organising pneumonia,
    • ILD associated with connective tissue diseases eg RA, scleroderma, polymyositis
    • Granulomatous ILD eg sarcoidosis
    • Other forms, eg histiocytosis X, eosinophilic pneumonias

Presentation tends to be:
  • progressive breathlessness with exercise
  • persistent non-productive cough

  • CXR - may be normal; may show increased reticular markings, ground glass abnormalities or nodular opacities
  • HRCT 
    • honeycombing - pulmonary fibrosis
    • ground glass changes - hypersensitivity pneumonitis
    • distribution of changes can also help diagnosis
  • lung function tests 
    • most commonly show a restrictive pattern with decreased lung volume and diffusing capacity for carbon monoxide
    • however patterns can vary
  • bronchoscopy
    • can help exclude infections
    • transbronchial biopsies - may diagnose sarcoidosis/hypersensitivity pnuemonitis
  • surgical biopsy
    • most commonly via VATS (video-assisted thoracic surgery)

  • pulmonary rehabilition
  • smoking cessation
  • ? oxygen therapy
  • details depend on the type of interstitial lung disease, for example:
    • idiopathic pulmonary fibrosis - ?  N-acetylecysteine
    • sarcoidosis - ?prednisolone if pulmonary function badly affected
    • hypersensitivity pneumonitis - avoidance of allergen

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